PHOENIX (AP) -- A trio of Arizona congressmen on Tuesday called for the head of the Phoenix Veterans Affairs Health Care Center to step down amid allegations of gross mismanagement and neglect at the facility, the latest in a string of issues at VA hospitals across the nation.

The call from Republican Reps. David Schweikert, Matt Salmon and Trent Franks comes after weeks of growing outrage about lapses in veteran patient care in Phoenix. They urged hospital director Sharon Helman and her leadership team to resign, saying in a letter that "drastic changes need to be made to ensure that this never happens again."

"In order to begin to restore faith in the veteran's health care system, department executives who were aware of and presided over this unethical and alarming mismanagement must be held accountable," they wrote.

The group also sent a letter to Veterans Affairs Secretary Eric Shinseki asking him to remove Helman and her leadership team.

The Phoenix VA has been under fire since the chairman of the House Veterans Affairs Committee said on April 9 that up to 40 patients may have died because of care delays and that the hospital kept a secret list of patients waiting for appointments to hide delays in treatment.

The U.S. Office of Inspector General is investigating the allegations, which come amid problems at other VA hospitals across the country. Patients are being forced to wait weeks and months to see doctors, and in some cases, dying before their appointments. In the past year, VA facilities in South Carolina, Florida, Georgia and Washington state have been linked to delays in patient care or poor oversight.

The Phoenix office for the Department of Veterans Affairs said in a statement Tuesday that the agency is "committed to delivering the highest quality care to veterans" and that it "takes these allegations seriously." The office also said it welcomes the results of the inspector general's investigation.

Dr. Samuel Foote, who had worked for the Phoenix VA for more than 20 years before retiring in December, brought the allegations to Congress and claims his complaints to his supervisors were ignored.

Rep. Jeff Miller, R-Fla., the chairman of the House Veterans Affairs Committee, said in an interview Tuesday that Foote was intimately involved in patient care in Phoenix.

"He has no ax to grind with the VA," Miller said. "I think he tried to bring this to the attention of executives and basically was shunned and felt the need to raise it to a higher level."

President Barack Obama on Monday said his administration is determined to find out whether veterans were denied help they needed at the Phoenix VA facility. He said he ordered Shinseki to investigate the allegations that care delays led to deaths.